A Study on a Functional Emulsion Coating and Infrared Laser-Induced Imaging Performance

Abstract

In isopropanol-water mixture, a polymer emulsion was prepared through the radical copolymerization [1,2] of styrene, acrylonitrile and 4-vinyl pyridine in the presence of azodiisobutyronitrile (AIBN) and a reactive emulsifier which was synthesized through the addition reaction of 2-isocyanatoethyl methacrylate and methoxypolyethylene glycols (Mn ≈ 2000). The polymer particles were narrowly distributed and had an average size of about 110 nm in diameter. Hydroxypropyl cellulose was used as the binder resin for the emulsion film. The emulsion coating was prepared by coating the mixture of the polymer emulsion and the water solution of the binder resin on aluminum substrate and dried at about 80°C. The resulted film can be easily removed from the substrate with water rinsing. However, once the coating is heated at a temperature which is much higher than the glass transition temperature (Tg) of the particle polymer (e.g., 150°C) for a short period of time, it could no longer be removed from the substrate by water. On the basis of the above work, a water soluble infrared-absorbing dye (IR dye) was incorporated into the emulsion coating and exposed to computer-controlled IR laser (830nm) scanning. The exposed areas could not be removed with water cleaning, whereas the non-exposed areas could still be easily removed with water. Negative images were obtained. Hence, the emulsion coating can be used in developing chemical-free CTP plates required by green printing industry.